In the practice of Dentistry, it is common to use a jet of fluid to irrigate or wash an operational area, followed by removal of the fluid and entrained debris by aspirating with a strong vacuum. This practice is suitable for cleaning durable areas such as tooth surfaces but must be moderated when cleaning within confined spaces such as in root canals or endodontic treatment, or around delicate tissues such as around the tooth, under the gums or periodontal treatment.
The irrigation of root canal preparations is complicated by the opening ("apical foramen") in the tip of the root(s) through which enter the structures that sustain the pulpal tissues. The apical third (root tip third) of the root canal systems are extremely complicated with an infinite variety of branching much like the delta system of rivers, or the branching of trees from the trunk. Another complication that has been established is that the proper cleansing and sealing of the apical third of root canal systems is the primary criterion for success of the endodontic therapy and the perpetuation and function of the tooth receiving the endodontic therapy.
In the endodontic treatment of root canal systems, it has been clinically established that the root canal systems must be cleansed as thoroughly as possible during the preparation of the primary root canal(s) for filling. It has also been demonstrated that the root canal preparation instruments do not, of themselves, reasonably thoroughly cleanse the primary root canal(s), and that it is not only desirable, but essential, that the root canal preparations be thoroughly irrigated with various chemical solutions designed to remove any remaining pulpal tissues, bacteria, toxins and debris resulting from the action of the root canal preparation instruments on the dentinal wall of the root canal preparation.
If, during the course of preparing the root canal system, preparation instruments are thrust through the apical foramen or, similarly, if irrigating solutions and debris are extruded through the apical foramen, then the periapical tissues surrounding the apical foramen and root of the tooth become inflamed and/or infected which can create intense pain for the patient and may require surgical intervention, or the loss of the tooth.
Thus a primary requirement for endodontic irrigation is to provide blocking or occluding of the apical foramen to prevent the extrusion of debris, irritants or other contaminants from the root canal into the periapical tissues during irrigation.
A tooth can be thought of as a bottle with a narrow neck, turned upside down in the jawbone. The root canal system in a tooth occupies a space very much like the neck of such a bottle. The most critical area of a root canal preparation in endodontics is the apical three to five millimeters of the root tip, i.e., the neck of the bottle in this simile.
The most difficult area to prepare and cleanse in root canal therapy is the apical end of the canal, not only due to its small diameter, but because of the curvature of roots which can be pronounced in some teeth. In addition, the mechanical limitations of most instruments presently available to prepare the root canal system actually work against the precise preparation of the apical third of the root. Consequently, the apical portion is almost invariably the least clean area of the root canal preparation, and most root canals contain debris in the apical third of the root. The cleanliness and seal of the apical third is the most important determinant of the success of root canal treatment.
The present most commonly employed devices for root canal irrigation are blunt hypodermic needles, or blunt hypodermic needles in which half of the cannula wall has been removed for a distance of 4 or 5 millimeters from the tip. Not only are such devices limited by their external diameter, but such devices have no provisions, whatever, to permit them to be placed in the apical termination of the root canal preparation to shield or close off the apical foramen to avoid forcing irrigating solution and debris into the surrounding periapical tissues. Consequently, these devices typically cannot be placed any further into the root canal preparation than the middle third and the irrigating stream pressure must be drastically reduced to avoid extrusion through the apical foramen. Additionally, the head of the irrigating stream tends to force debris into the apical third. The result is that these devices fail to reasonably and thoroughly irrigate and cleanse the apical third of root canal preparations.
The failure of prior art root canal preparation instruments to reasonably and thoroughly clean the critical apical third of root canal preparations, coupled with the inability of present irrigating delivery devices to be placed in the apical termination of fine or tortuous root canal systems, often results in the sealing of debris laden apical thirds of root canal preparations with a termination diameter of 0.30 millimeters or less. Thus, root canal irrigation is the most neglected phase of endodontic therapy, especially in fine, tortuous root canals.
Upon completion of the irrigating process, irrigating solutions, which remain in the root canal preparation(s), must be removed, since it is desirable that the root canal preparation be as dry as possible prior to sealing and filling the root canal preparation.
Presently used are ordinary hypodermic needles and syringes that cannot be efficiently placed in the apical third, or rolled, tapered paper cones that require tedious, numerous placement and removal to absorb the moisture, and which may act to tamp debris into the critical apical third of the root canal preparation.
Again, the apical foramen must be shielded to avoid tamping debris through the apical foramen (as with the paper cones) and creating irritation, inflammation and/or infection in the periapical supportive tissues or suctioning bacteria or tissue elements through the apical foramen into the critical apical third, thereby possibly contaminating the critical apical third region.
Efforts to enhance the irrigation and aspiration of the irrigating solution from tooth surfaces, cavities and especially roots are evident in the prior art. U.S. Pat. No. 3,624,907 (Brass et al.) discloses a device for irrigating and simultaneously aspirating the irrigation fluid from tooth cavities, including root canals. Brass discloses a small diameter tube which is inserted into the tooth and a handle connected to the tube which switches the handle end of the tube alternately to either a supply of irrigating liquid or a source of vacuum for aspirating the liquid out of the tooth cavity. The tube disclosed by Brass necessarily must be of a small external diameter in order to reach into the tooth cavity. This small external diameter limits the opening inner diameter of the tube through which the liquid and any debris from the therapy is withdrawn from the cavity. The external diameter of the tube limits the ability of the practitioner to insert the tube into the apical third of the canal. The smaller diameter of the tube opening limits the size of the debris particle which may be withdrawn through the tube. Brass does not suggest how larger debris particles may be withdrawn nor how the instrument may be inserted into the apical third of the canal.
U.S. Pat. No. 3,749,090 (Stewart) discloses an instrument for alternatively delivering fluid to a surgical site and removing fluids from the site by vacuum aspiration. Stewart discloses a handle attached to removable hollow tubes which may be sterilized for use in aseptic procedures. Stewart teaches that such an instrument is suitable for surgical procedures but does not suggest how it may be adapted for use in extremely small surgical procedures such as root canal therapy.
U.S. Pat. No. 3,164,153 (Zorzi) discloses an instrument adapted for delivering a liquid to an oral operating site and alternatively aspirating liquids from the site through tubes by use of a compressed air system commonly available to dental practitioners. The needle-like tubes described by Zorzi have an inner opening diameter determined by the exterior dimension of the needle and the wall thickness thereof. Zorzi does not suggest how the exterior dimension may be reduced to readily reach into the apical region of a tooth root canal nor how the inner opening diameter may be increased to allow the passage of debris particles from the canal.
U.S. Pat. No. 4,340,365 (Pisanu) discloses a larger instrument for cleaning work areas such as the oral cavity. Pisanu increases the opening of the aspirating tube by placing it circumferentially around the outside of a smaller inner tube which serves to direct the cleansing liquid into the operating site. The instrument disclosed by Pisanu may be made large enough to aspirate larger debris particles but is then too large to be inserted into the tooth root canal. The smaller liquid delivery tube may force a jet of liquid into the apical portion of the canal which may carry with it debris particles which may become lodged in the small passages of the canal, preventing their aspiration by the larger tube.
U.S. Pat. No. 4,215,476 (Armstrong) discloses how an instrument for delivering and aspirating liquids may be joined through a suitable handpiece to a source of several fluid reservoirs. Armstrong utilizes concentric tubes to deliver the fluid and aspirate it from the operation site as is customary in the present art. Armstrong does not, however, address the miniaturization of the instrument in order to reach the innermost portion of small operating areas such as the apical third of a tooth root canal preparation.
Each of the above described instruments for lavage and aspiration in the field of endodontics suffer from the same limitations due to size of the tip portion to be inserted into the tooth cavity. As the external dimension is reduced to allow insertion of the instrument further into a root canal, the inner opening dimension is reduced to a point where the opening is too small to allow the passage of debris particles.
Perhaps the safest and most effective device of this kind is that of U.S. Pat. No. 4,276,880, in which the device has a closed, rounded tip designed to close off the apical foramen with a precise side-window design, all as integral in one cannula that effectively disperses the impact force of the fluid irrigating stream, while creating a highly turbulent cleansing action of the irrigating solution. This device adequately answers the irrigating requirements for root canal preparations that have a root canal preparation termination diameter of 0.30 millimeters or larger. However, there are many root canal preparations that may vary in the root canal termination diameter from 0.10-0.25 millimeters, in which this device cannot be seated due to the limitations of the external diameter of the device. The device could be produced in a smaller external diameter except for the fact that the present smallest external diameter of manufactured metal cannula tubing is approaching the manufacturing limits of ensuring that a patent internal channel (lumen) is maintained in the metal cannula tubing. Manufacturing capabilities, presently, do not make it possible to produce realistic and economically feasible cannula tubing of an external diameter less than 0.30 millimeters having a realistic internal diameter of the lumen, nor can this be overcome by the presently available extrusion or molding processes for hollow plastic tubing.
In periodontal irrigation, it is necessary to avoid injury to the delicate epithelial and connective tissue attachments joining the tooth root to the bone when a cannula or tube carrying the irrigating fluid is placed on the bottom of the sulcus or the periodontal pocket. Thus, as the means of obstructing the apical foramen assumes a broad coverage to assure maximum sealing of the foramen by the intraprobe cannulas, in a similar manner, the delicate attachments of the periodontal tissues connecting the tooth and bone require a comparatively broad contact surface to distribute the force of the irrigating fluid and instrument contact in order to minimize the potential of penetration of the epithelial and connective tissue attachments by the irrigating/aspirating intraprobe cannulas.
Although the hydraulic principles are comparable in endodontic and periodontal subgingival irrigation, several problems are inherently unique to periodontal subgingival irrigation. First, the delicate epithelial and connective tissue attachments must be spared from tearing or laceration by any subgingival irrigating device, and, secondly, the impact force of the irrigating stream must be sufficiently dispersed so as not to impact bacteria, toxins, calculus or other debris into the surrounding soft tissues. Further, the impact force of the irrigating stream must not create a stripping or tearing of the delicate attachment tissues.
Prior art devices used for subgingival irrigation comprise various forms of open-ended cannulas (such as blunted hypodermic needles) used with hand syringes, or oral irrigation devices, and various forms of tapered tips attached to oral irrigating devices.
All of these have serious limitations both as to tearing and lacerating tissues by the edges or tips of the devices, and because the narrowing of the irrigating passages concentrates the impact force of the irrigating stream finally emerging from the open end of the devices in a manner potentially comparable to the effects of a miniature "water cannon," which can blast away the delicate tissue attachments and impact bacteria, toxins, calculus and other debris into the vulnerable connective-supportive tissues.
The device disclosed by U.S. Pat. No. 4,276,880, discussed above, includes a smooth, rounded, closed end which prevents tearing or laceration of the tissues by the tip or end of the device. A side-window design disperses the impact of the fluid stream into a gentle, "shower-like," highly turbulent cleansing flow. The limitation of this device is that it is expensive to manufacture, requires a manufacturing capability of the highest tolerances and cannot be utilized in root canal preparations of the smaller diameters.